1. Field of the Invention
The present invention relates to fluid flow monitoring devices, and more particularly to a device of the type having a vane member positioned in a fluid flow path for movement to positions which vary in accordance with the fluid flow rate.
2. Description of the Prior Art
Existing fluid flow meters typically have a housing defining a fluid flow path and a vane positioned within the path so that it moves to positions which vary depending on the rate fluid flows in the path.
An indicator, for example the pointer of a gauge, is commonly positioned within the housing and coupled to the vane either mechanically, or by an arrangement of permanent magnets, to provide an indication of the vane position and hence of the fluid flow rate. However, this often proves unsatisfactory because in many cases the housing must be placed at locations, for example under the hood of a vehicle, making the indicator inaccessible for convenient monitoring.
In addition, various types of mechanisms requiring moving mechanical linkages, such as rotating shafts, have been suggested for coupling the vane to an indicator which is remote from the housing. In addition to the complexity, bulky size, and cost of such systems, expensive seals are required to make the housing fluid tight at the point where the moving shaft or other linkage passes from the interior to the exterior thereof.
Another common drawback of existing flow meters are the numerous moving parts which may jam and make the devices inoperable until time consuming repairs are completed. Furthermore, such devices often lack reliability because there is no provision for fluid flow in the event the fluid flow path becomes obstructed, as when the vane becomes jammed.
Moreover, existing devices are not easily adaptable for a wide range of flow monitoring operations.
One type of flow meter utilizing a transformer is disclosed in the Manual of Electromechanical Devices (citation below). However, this device also suffers from many of the deficiencies noted above.
Flow metering devices illustrative of the known prior art and of the foregoing problems are disclosed in U.S. Pat. Nos. 2,939,319; 2,892,348; 2,724,969; 2,248,030; 2,029,633; 3,224,270; 3,282,102; 3,393,563; 3,559,197; and on page 314 of the Manual of Electromechanical Devices by Douglas C. Greenwood, published in 1965 by McGraw-Hill, Inc.